METAL MATRIX COMPOSITE USEFUL AS WEAR PARTS FOR CEMENT AND MINING INDUSTRIES

Description

Technical field

[0001] The present invention generally relates to cast metal matrix composites, uses thereof and methods for the preparation thereof.

Background Art

[0002] Wear parts are used in many industries such as cement and mining industries. The metal matrix composites used as wear parts have to comply with several requirements in order to be efficient. The wear parts are usually implemented within mining equipment intended to crush and grind the solid material. Thus, they have to show a good resistance to the impacts and the abrasion to which they are subjected during their use. Ductile materials show improved resistance to impact but low resistance to abrasion whereas hard abrasion-resistant materials provide a satisfying resistance to abrasion but low resistance to violent impacts. Thus, it is critical to develop a cast metal matrix composite showing a good balance between the resistance to the abrasion and the impacts. Furthermore, the wear parts are consumable materials involving their frequent replacements. It is essential that the replacements of these wear parts be spaced out, easy and cost less. The production costs of the wear parts have to be low for being implemented in the industry.

[0003] US 2008/102300 A1 relates to metal matrix ceramic composite (MMCC) wear-parts comprising a wearing portion formed by a ceramic cake impregnated by metal. The ceramic cake comprises ceramic grains and carbide grains. The invention also relates to a method for manufacturing the wear-parts. The invention further describes a grinding roll and a table liner for a vertical mill each comprising a metal matrix ceramic composite wear part(s) of the invention.

Technical problem

[0004] The present invention aims to provide a reinforced cast metal matrix composite useful as wear parts for cement and mining industries. The present invention also intends to provide wear parts showing an extended life service with high production rates while having low production costs.

General Description of the Invention

[0005] The cast metal matrix composite according to the present invention comprises two distinct parts namely:

• One or more ceramic cakes comprising: Al₂O₃, ZrO₂, ferrous metal and TiC, wherein the ceramic cakes comprise from 30 to 60 wt% of Al₂O₃, from 20 to 40 wt% of ZrO₂, from 0,2 to 4 wt% of graphite, from 1 to 20 wt% of FeTi and from 3 to 6 wt% of binder compared to the total weight of the ceramic cakes before pouring the metal matrix and wherein they comprise from 2 to 10 vol% of TiC after pouring the metal matrix with respect to the total volume of metal in the ceramic cake after pouring the metal matrix,
• and a metal matrix comprising: ferrous metal and TiC, wherein the metal matrix comprises from 50 to 90 wt% of ferrous metal compared to the total weight of the metal matrix and from 0,1 to 10 vol% of TiC compared to the total volume of the metal matrix.

[0006] It is one aspect of the invention to provide a cast metal matrix composite, which comprises TiC both in the ceramic part and in the metal matrix.

[0007] The ceramic cakes correspond to the hard material of the cast metal matrix composite. The ceramic cakes are preformed before being included within the metal matrix. These ceramic cakes show a high hardness due to their composition comprising, in particular, a mixture of TiC and inorganic compounds: Al₂O₃ and ZrO₂.

[0008] The metal matrix includes a ferrous metal and TiC. The presence of TiC allows reinforcing the matrix of metal. Indeed, the inventors have noted that the reinforcement of the metal matrix with TiC allows obtaining a better resistance of the ceramic cakes within the metal matrix. It means that the ceramic cakes are maintained more strongly within the metal matrix and thus are more hardly removed from it when submitted to the use conditions. Indeed, the presence of TiC within the metal matrix increases its hardness, but does not affect the fracture toughness. The obtained material is thus more wear resistant without increasing the risk for cracking. Furthermore, the inventors surprisingly found out that the insertion of the ceramic compounds (Al₂O₃ and ZrO₂) is improved when the metal matrix also comprises TiC.

[0009] Another aspect of the invention concerns the method for the preparation of the cast metal matrix composites. The metal matrix composite according to the present invention is prepared by a casting process. Such a process offers several advantages since it is economical and easy to implement. Furthermore, the formation of TiC within the ceramic cakes occurs during the casting process namely during the pouring step of the metal matrix .The addition of the melt metal matrix upon the ceramic cakes leads to the formation of TiC within the ceramic cakes. Indeed, titanium and carbon are very reactive components and lead to the production of TiC when they are mixed at temperatures above about 1100°C. The particles of TiC obtained show a diameter/size of inferior or equal to about 30 microns. Furthermore, these particles are homogenously distributed within the metal matrix. The formation of the TiC particles leads to an increase in strength, strain and hardness of the material obtained, which in turn allows improving its service lifespan and its wear resistance.

[0010] In this context, it has to be noted that it would not be possible to add directly this kind of TiC particles (i.e. with the same diameter size) within the metal matrix while benefitting from the same effects. Indeed, even if particles of that size were added, they would coagulate and the metal would not cover them in the way provided by the present method. Such a coagulation and inappropriate covering would be deleterious for the properties of the wear resistant material.

[0011] The process of preparation according to the present invention preferably comprises a step of preformation of the ceramic cakes followed by a step of casting a metal matrix. In particular, the method of preparation may thus include the steps of:

(a) preparing the ceramic cake(s) by:

• mixing Al₂O₃, ZrO₂, FeTi , graphite and a binder,
• filling the mixture obtained in preform mold(s),
• heating and curing the mixture,
• removing the (preformed) ceramic cakes obtained from the preform mold(s),
• cooling down the mixture to room temperature,

(b) casting the ceramic cake(s) into a composite by:

• placing the (preformed) ceramic cakes in resin type mold(s)
• closing the resin type mold(s),
• melting metal comprising ferrous metal and ferrotitanium and graphite in order to obtain an alloy of metals comprising TiC,
• pouring the alloy of metals in the resin type mold(s)
• obtaining a cast metal matrix composite.

[0012] Another aspect of the invention concerns an article comprising the use of cast metal matrix composites according to the present invention and in particular wear parts.

Brief Description of the Drawings

[0013] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

Fig. 1 shows a ceramic cake having a honeycomb shape.

Fig. 2 shows a detail of the ceramic cake having a honeycomb shape before pouring the metal matrix.

Fig. 3 shows a view of a cast metal matrix composite according to the present invention wherein ceramic cakes are included within a metal matrix.

Fig. 4 shows portions comprising ceramic cake and a metal matrix in a suitable shape, namely adapted to be inserted within a further metal layer.

Fig.5 shows a specific embodiment of the present invention wherein portions of cast metal matrix composite (such as those of Fig. 4) are included within a further (preferably ductile) metal. Fig.5-A shows this embodiment wherein the portions are visible by transparency within the (preferably ductile) metal. Fig.5-B is another view of this embodiment wherein the parts of the portions included within the (preferably ductile) metal are hidden.

[0014] Further details and advantages of the present invention will be apparent from the following detailed description of several non limiting embodiments with reference to the attached drawings.

Description of Preferred Embodiments

[0015] The present invention proposes a cast metal matrix composite which comprises ceramic cakes included within a metal matrix. In particular, this cast metal matrix composite is reinforced by the simultaneous presence of TiC in the ceramic cakes and the metal matrix.

[0016] The cast metal matrix according to the present invention comprises:

• one or more ceramic cakes comprising: Al₂O₃, ZrO₂, ferrous metal and TiC, wherein the ceramic cakes comprise from 30 to 60 wt% of Al₂O₃, from 20 to 40 wt% of ZrO₂, from 0,2 to 4 wt% of graphite, from 1 to 20 wt% of FeTi and from 3 to 6 wt% of binder compared to the total weight of the ceramic cakes before pouring the metal matrix and wherein they comprise from 2 to 10 vol% of TiC after pouring the metal matrix with respect to the total volume of metal in the ceramic cake after pouring the metal matrix, and
• a metal matrix comprising : ferrous metal and TiC, wherein the metal matrix comprises from 50 to 90 wt% of ferrous metal compared to the total weight of the metal matrix and from 0,1 to 10 vol% of TiC compared to the total volume of the metal matrix.

[0017] TiC which is present within the ceramic cakes and the metal matrix is obtained through the following in situ reaction: FeTi+C which converts to Fe+TiC. This reaction is obtained by contacting the reagent materials at high temperatures, namely at temperatures over about 1100°C.

[0018] It is advantageous to use TiC since it shows a very high hardness value over 3000 HV and is stable in ferrous solutions.

[0019] Regarding the ceramic cakes, it has to be noted that the in situ reaction for producing TiC occurs only at the time the metal matrix comprising ferrous metal and TiC is poured onto the ceramic cakes. When pouring the metal matrix, the metal matrix comprising the ferrous metal and TiC infiltrates within the ceramic cakes and fills the gaps between the ceramic grains. Thus, the ceramic cakes are loaded with the metal matrix. This leads to the formation of TiC within the ceramic cakes. As a result, the weight of metal matrix included within the ceramic cake corresponds to four times the weight of the ceramic cake.

[0020] Thus, before the pouring step, the (preformed) ceramic cakes comprise: Al₂O₃, ZrO₂, FeTi, graphite and a binder.

[0021] A binder is used, within the ceramic cakes, in order to aggregate the grains of ceramic. The binder used in the ceramic cake may be preferably an inorganic binder. In particular, the binder may be selected from the group comprising sodium silicate, colloidal silicate or a mixture thereof.

[0022] In particular, it has to be noted that the use of the colloidal silicate reduces the hygroscopic properties of the material obtained and thus avoids the increase of the moisture within the material. Indeed, this is due to the structure of the colloidal silicate which allows binding the sites which could be occupied by the water molecules. Contrary to other binders, the colloidal silicates limit the absorption of water (for example from the ambient air) by the ceramic cakes. Thus, the strength of the ceramic cakes does not decrease which prevents the formation of cracks. In order to limit the effects of water absorption by the binder, the known processes require the use of the ceramic cakes as fast as possible. Such processes do not allow the preformation of large quantities of ceramic cakes since they cannot be stored during a sufficiently long period. As a result, the use of colloidal silicate as a binder represents a preferred embodiment of the present invention with significant advantages since a large amount of ceramic cakes can be prepared well before the actual casting of the metal matrix, stored during extended periods and used as needed.

[0023] According to the present invention, the ceramic cake before the pouring step comprises from 3 to 6 wt% and preferably from 4 to 5 wt% of binder compared to the total weight of the ceramic cake.

[0024] Before the pouring step, the quantity of graphite is comprised between 0,2 and 4wt%, preferably from 0,5wt% to 3wt% and preferably from 0,875wt% to 2,625wt% compared to the total weight of the ceramic cake.

[0025] Before the pouring step, the ceramic cake comprises 1 to 20 wt% of FeTi and preferably from 5 to 15wt% compared to the total weight of the ceramic cake.

[0026] The ceramic cake also comprises from 30 to 60 wt% and preferably from 40 to 55 wt% of Al₂O₃ compared to the total weight of the ceramic cake.

[0027] The quantity of ZrO₂ is comprised between 20 and 40 wt% and in particular between 25 and 35 wt% compared to the total weight of the ceramic cake.

[0028] According to the present invention, the ceramic cake comprises from 30 to 60wt% of Al₂O₃, from 20 to 40wt% of ZrO₂, from 0,2 to 4wt% of graphite, from 1 to 20wt% of FeTi and from 3 to 6wt% of binder compared to the total weight of ceramic cake before the pouring step.

[0029] After the pouring step of the metal matrix, the ceramic cake comprises from 2 to 10vol% of TiC and preferably from 4 to 8vol% of TiC.

[0030] The ceramic cakes may have any shape allowing the filling of the metal in the gaps between the ceramic particles, in particular the ceramic cakes may have a honeycomb shape (1) as shown in Fig.1. Indeed, it has been noted that such a shape is particularly suitable for the use according to the present invention. In fact, when casting the metal matrix, the metal can easily and quickly infiltrate each cavity of the ceramic cake (1), whereas without such shape, the metal matrix could solidify before entirely filling the cavities of the ceramic cake. This shape therefore allows a better infiltration of the metal matrix. Fig.2 shows a detailed view of this honeycomb (preform) ceramic cake (1) before pouring the metal matrix, which thus comprises Al₂O₃, ZrO₂ (corresponding to grains of ceramic (2)), FeTi (3) and graphite (4).

[0031] The cast metal matrix composite according to the invention may comprise a plurality of ceramic cakes, wherein the ceramic cakes have a honeycomb shape.

[0032] Regarding the metal matrix, it comprises a ferrous metal. Ferrous metals can be defined as metals which comprise a largest part of metal(s) comprising iron (Fe), for example: steels, cast irons and their alloys with other metals. According to one embodiment, the ferrous metals can be selected from: High Chromium Iron (like for example ASTM A532 Class 2 type E), Chromium steel (like for example DIN 1.2601), Ni hard metals (like for example ASTM A532 Class 1 type D) or low alloy steel (like for example DIN 1.2356) and combinations thereof.

[0033] The metal matrix includes from 50 to 90 wt% and preferably from 60 to 85 wt% of ferrous metal compared to the total weight of the metal matrix. In addition, the metal matrix also includes TiC. Preferably, TiC is comprised from 0,1 to 10 vol%, and in particular from 2 to 6 vol% compared to the total volume of the metal matrix.

[0034] The metal matrix comprises from 50 to 90wt% of ferrous metal compared to the total weight of the metal matrix and from 0,1 to 10vol% of TiC and in particular from 2 to 6 vol% of TiC compared to the total volume of the metal matrix.

[0035] According to one embodiment, the cast metal matrix composite comprises from 2 to 10 vol% of TiC, preferably from 4 to 8 vol% TiC, and preferably about 6 vol% TiC with respect to the total volume of metal in the ceramic cake after pouring the metal matrix. It has been identified that wear resistance of ferrous metal casting will be improved by increasing the volume% of TiC up to 6vol%. In fact, a wear resistance peak has been observed at about 6vol% whereas TiC is still homogeneously distributed in ferrous matrix.

[0036] Fig.3 shows a cross-section of a cast metal matrix composite (5) according to one embodiment of the present invention. The ceramic cakes (1) are placed in a resin-type mold. A metal matrix (6) has been poured within the ceramic cakes in order to fill the resin-type mold. Thus, it is obtained a cast metal matrix composite (5) comprising ceramic cakes (1) embedded within a metal matrix (6).

[0037] According to one embodiment of the present invention, the cast metal matrix composite can also comprise an additional metal, in particular a ductile metal. This metal can be selected among the ductile irons. As a result, such cast metal matrix composite would include one ceramic cake and two metals. The ductile metal improves the toughness of the cast metal matrix composite material and allows rendering the material more resistant to shocks and breaking.

[0038] The cast metal matrix composite according to the present invention can be used as wear parts for cement and mining industries.

[0039] The present invention also concerns an article comprising the cast metal matrix composite according to the present invention such as: wear parts. The wear parts comprising the cast metal matrix composite can be used in general in plants for grinding, crushing and conveying various abrasive materials; in mining and construction equipments such as bucket wheel excavators, dragline excavators, high capacity haulage trucks, and crushing/milling machines; in industries such as cement factories, mines, metallurgy or electricity generating stations.

[0040] The article comprising the cast metal matrix composite according to the present invention may also be raw mill, coal mill, grinding mill castings, roller and table segments (or liners) for raw, coal, grinding mills, or crushers or kiln cooler parts.

[0041] According to the present invention, the method for producing the cast metal matrix composite includes two main steps. The first one (step (a)) concerns the preparation of the ceramic cakes preforms and the second one (step (b)) relates to the casting of the metal matrix upon the ceramic cakes.

[0042] It has to be noted that the second step (b) corresponds to a casting step which is convenient to implement and low-cost.

[0043] The preparation of the preformed ceramic cakes (step (a)) includes the steps of:

• mixing Al₂O₃, ZrO₂, FeTi, graphite and a binder,
• filling the mixture obtained in preform molds,
• heating and curing the mixture,
• removing the (preformed) ceramic cakes from the preform molds.
• cooling down the mixture to room temperature,

[0044] These steps are performed before the casting of the metal matrix.

[0045] According to one embodiment of the present invention: the preform molds are silicone core boxes. Indeed, such kinds of molds, which are very flexible, allow easily removing the ceramic cakes. The preform molds can be in honeycomb shape in order to facilitate the infiltration of the metal matrix when casting.

[0046] The heating step of the mixture may be performed with a microwave oven, an infrared oven or a conventional oven, such as a gas or electrical convection oven.

[0047] After being cooled at about room temperature (for example below 40°C), the ceramic cakes are ready to be subjected to the casting step (or stored until casting is performed).

[0048] It has to be noted that when the ceramic cakes comprise colloidal silicate as a binder, the method provides the additional advantage that the ceramic cakes can be prepared well before the casting of the metal matrix. The ceramic cakes can be preformed and stored during one week before being used for the preparation of the cast metal matrix composite. Thus, a large quantity of ceramic cakes can be prepared since they are not subjected to the constraint of being immediately used in the casting process.

[0049] The second step (b) of the process concerns casting the ceramic cakes into a composite.

[0050] In order to obtain a ceramic metal matrix composite, a metal matrix should be casted/poured upon the ceramic cakes in order to cover and to infiltrate them.

[0051] According to one embodiment, the ceramic cakes may be placed e.g. in resin-type molds, such as at the upper surface or the side surface of this resin-type mold. The density of the ceramic cake is lower than the density of the metal matrix. As a result, when pouring the metal matrix within the resin-type mold, the ceramic cakes are forced to float. During the pouring step, the ceramic cakes are heated up by hot air convection which allows an easy penetration of the metal matrix.

[0052] Any appropriate resin-type mold can be used for the preparation of the cast metal matrix composite, such as for example ALpHASET®, furan, sodium silicate or other sand molds. According to one embodiment of the present invention, the ceramic cakes can be screwed to the resin type mold with steel screws or otherwise affixed thereto.

[0053] Then, the resin-type mold is closed before pouring the metal matrix.

[0054] The metal matrix is prepared by mixing and melting (at least) ferrous metal with ferrotitanium and graphite. This step can be performed in a furnace such as an induction furnace. The ferrotitanium and the carbon should be preferably added within the mixture after the ferrous metal. In particular, the ferrotitanium can be added either into the furnace, in the ladle or directly in the resin-type mold. The advantage to add the ferrotitanium within the furnace is the possibility to use less expensive ferrotitanium which comprises only 30-50 wt% of Ti. Regarding the carbon or graphite, it is preferable to add it directly in the furnace. According to one embodiment of the present invention, the carbon is added in the furnace and the ferrotitanium is added in the ladle.

[0055] The pouring step should be performed at a temperature which is 250 to 300°C above the liquidus of the metal. The metal matrix should be poured in the resin-type mold in order to cover and to infiltrate the ceramic cakes and to cover the walls of the resin-type mold.

[0056] Additional fettling operations identical to the conventional ones may be implemented. The cast metal matrix composite may for example be subjected to an additional heat treatment.

[0057] According to one specific embodiment of the present invention, a further metal can be added to the cast metal matrix composite obtained through the above-mentioned method for improving its resistance to shocks. This metal should be selected among metals more ductile than that used in step (b), for example ductile irons. Thus, the method according to the present invention may further comprise an additional step (c) which involves:

• placing one or several portion(s) of the cast metal matrix composite obtained from step (b) in a further resin-type mold,
• pouring another metal in said resin-type mold.

[0058] In order to obtain the portions of the cast metal matrix composite (previously obtained), it may be carved up in suitable shapes. As a result, the cast ceramic metal matrix composite is in the shape of several portions.

[0059] Fig.4 shows portions (7) of cast metal matrix composite. These portions (7) are produced in a shape suitable for being included in another metal. As it is shown, these portions comprise the ceramic cakes (1) having a honeycomb shape which are filled with a metal matrix (6).

[0060] These portions obtained may be placed in a further resin-type mold for being subjected to a (further) casting step. For this embodiment, this resin-type mold should be heat resistant and could for example comprise sodium silicate. Once placed in the resin-type mold, the portions may be heated up before the pouring step. Then, the additional metal matrix is poured in the resin-type mold upon the portions. As a result, the portions are included within the ductile metal, thereby obtaining a cast metal matrix composite comprising ceramic cakes, a hard wear metal matrix and a ductile shock resistant metal. In fact, the ductile metal constitutes the carrier of the portions of cast metal matrix composites. Fettling operations may be further implemented and a heat treatment may be applied.

[0061] Fig.5A and B illustrate this specific embodiment. Fig.5-A shows this embodiment wherein the portions are visible by transparency within the (preferably ductile) metal whereas in Fig 5-B the parts of the portions which are included within the (preferably ductile) metal are not shown. Fig.5A and B show portions (7) of cast metal matrix composite which are arranged within another metal (8). These portions (7) have been obtained through steps (a) and (b) of the method described herein. These portions (7) are included within a layer of a further metal (8) which may be for example ductile iron. Thus, the composite obtained according to this embodiment (9) comprises both a wear resistant metal matrix composite (7) on the wearing side and shock resistant ductile iron (8) at the carrier side. The portions (7) are preferably spaced in such a way that the cast ductile iron (8) can be infiltrated between these portions.

[0062] It is to be noted that all previously mentioned embodiments may be combined where useful or desirable.

[0063] The following examples are provided for illustration purposes and should not be construed to limit the invention.

a) Examples of compositions of cast metal matrix

[0064] The following examples of metal matrixes have been produced by a method according to the present invention.

• ASTM A532 Class 1 type D + (0-4 % Titanium + (0,25* %Ti) % Carbon).
• ASTM A532 Class 2 type B + (0-4 % Titanium + (0,25* %Ti) % Carbon).
• ASTM A532 Class 2 type C + (0-6 % Titanium + (0,25* %Ti) % Carbon).
• ASTM A532 Class 2 type D + (0-6 % Titanium + (0,25* %Ti) % Carbon).
• ASTM A532 Class 3 type A + (0-4 % Titanium + (0,25* %Ti) % Carbon).

b) Examples of a supplementary (ductile) metal

[0065] ASTM A536 80-60-03 (American standard) or ISO 1083 600-3 (International standard) or similar.

c) Example of a cast metal matrix composite

- Inside and around the ceramic cake (after the pouring step)

[0066] 

• Alumina (Al₂O₃): 10 wt%,
• Zirconia (ZrO₂): 6 wt %,
• Titanium Carbide (TiC): 4 wt% (2,65% of TiC coming from metal and 1,35% of it coming from cake, this also corresponds to 6 vol%),
• Ferrous Alloy: 80 wt%.

- Metal matrix

[0067] 

• C: 3,66 wt%,
• Si:0,63 wt%,
• Mn: 1,3 wt%,
• Cr: 18,5 wt%,
• Mo: 1,5 wt%,
• Cu: 0,8 wt%,
• Ni:0, 4 wt%,
• Ti: 2,12 wt%. [in fact, 2,12% of Ti is equivalent to 2,65% of TiC (0,53% being C)]

[0068] All the cast metal matrix composites according to the present invention show a very good wear resistance. The presence of TiC in both ceramic cakes and metal matrix allows increasing the hardness of the cast metal matrix composites without affecting its fracture toughness. Furthermore, it appears that the ceramic compounds are homogeneously distributed within the metal matrix.

Claims

1. A cast metal matrix composite including:

- one or more ceramic cakes comprising: Al₂O₃, ZrO₂, ferrous metal and TiC, wherein the ceramic cakes comprise from 30 to 60 wt% of Al₂O₃, from 20 to 40 wt% of ZrO₂, from 0,2 to 4 wt% of graphite, from 1 to 20 wt% of FeTi and from 3 to 6 wt% of binder compared to the total weight of the ceramic cakes before pouring the metal matrix and wherein they comprise from 2 to 10 vol% of TiC after pouring the metal matrix with respect to the total volume of metal in the ceramic cake after pouring the metal matrix, and

- a metal matrix comprising: ferrous metal and TiC, wherein the metal matrix comprises from 50 to 90 wt% of ferrous metal compared to the total weight of the metal matrix and from 0,1 to 10 vol% of TiC compared to the total volume of the metal matrix.

2. The cast metal matrix composite according to claim 1 wherein TiC of the ceramic cake(s) and of the metal matrix is produced through an in situ reaction of FeTi+C, which leads to the formation of Fe+TiC.

3. The cast metal matrix composite according to any one of claims 1 to 2 wherein the ferrous metal is High Chromium Iron, Chromium steel, Ni hard metals or low alloy steel.

4. The cast metal matrix composite according to any one of claims 1 to 3 comprising a plurality of ceramic cakes and wherein the ceramic cakes have a honeycomb shape.

5. The cast metal matrix composite according to any one of claims 1 to 4 wherein the metal matrix comprises from 2 to 6 vol% of TiC compared to the total volume of the metal matrix.

6. The cast metal matrix composite according to any one of claims 1 to 5 wherein it comprises further metal(s).

7. The cast metal matrix composite according to claim 6 wherein the further metal(s) is/are selected from ductile metals.

8. An article or apparatus comprising cast metal matrix composite(s) according to any one of claims 1 to 7.

9. Use of a cast metal matrix composite according to any one of claims 1 to 7 or of an article according to claim 8 as wear parts, in particular for cement and mining industries.

10. A method for the preparation of the cast metal matrix composite according to any one of claims 1 to 7 comprising the following steps:

(a) preparing ceramic cake(s) by

- mixing Al₂O₃, ZrO₂, FeTi, graphite and a binder, wherein the binder preferably is an inorganic binder, more preferably comprising sodium silicate, colloidal silicate or a mixture thereof,

- filling the mixture obtained in preform mold(s),

- heating and curing the mixture, preferably by heating with a microwave oven, an infrared oven or a conventional oven,

- removing the ceramic cakes from the preform mold(s),

- cooling down the mixture to room temperature,

(b) casting the ceramic cake(s) into a composite by

- placing the ceramic cake(s) in a resin-type mold,

- closing the resin-type mold,

- melting metal comprising ferrous metal and ferrotitanium and graphite in order to obtain an alloy of metals comprising TiC,

- pouring the alloy of metals in the resin-type mold,

- obtaining a cast metal matrix composite.

11. The method according to claim 10 which further comprises an additional step (c) comprising:

- placing one or several portion(s) of the cast metal matrix composite obtained from step (b) in a further resin-type mold,

- pouring a further metal matrix in the resin-type mold.

12. The method according to claim 11 wherein it comprises a step of:

- heating the portion(s) of the cast metal matrix composite in the resin-type mold before the pouring step.

13. The method according to claim 10 or 12 which further comprises the steps of:

- implementing fettling operations.

14. The method according to claim 13 which further comprises the step of:

- applying a heat treatment to the cast metal matrix composite obtained.

15. The method according to claim to any one of claims 10 to 14 wherein the preform molds are silicon core boxes.

Ansprüche

1. Metallguss-Matrix-Verbundwerkstoff, der Folgendes umfasst:

- einen oder mehrere Keramikkuchen, umfassend: Al₂O₃, ZrO₂, Eisenmetall und TiC, wobei die Keramikkuchen 30 bis 60 Gew.-% Al₂O₃, 20 bis 40 Gew.-% ZrO₂, 0,2 bis 4 Gew.-% Graphit umfassen, 1 bis 20 Gew.-% FeTi und 3 bis 6 Gew.-% Bindemittel im Vergleich zum Gesamtgewicht der Keramikkuchen vor dem Gießen der Metallmatrix und wobei sie zwischen 2 und 10 Vol.-% TiC nach dem Gießen der Metallmatrix im Hinblick auf das Gesamtvolumen an Metall in dem Keramikkuchen nach dem Gießen der Metallmatrix umfassen, und

- eine Metallmatrix, umfassend: Eisenmetall und TiC, wobei die Metallmatrix 50 bis 90 Gew.-% Eisenmetall im Vergleich zum Gesamtgewicht der Metallmatrix, und 0,1 bis 10 Vol.-% TiC im Vergleich zum Gesamtvolumen der Metallmatrix umfasst.

2. Metallguss-Matrix-Verbundwerkstoff gemäß Anspruch 1, wobei das TiC des/der Keramikkuchen(s) und der Metallmatrix durch eine In-Situ-Reaktion von FeTi+C hergestellt wird, was zur Bildung von Fe+TiC führt.

3. Metallguss-Matrix-Verbundwerkstoff gemäß einem der Ansprüche 1 bis 2, wobei es sich bei dem Eisenmetall um hochchromhaltiges Eisen, Chromstahl, Ni-Hartmetalle oder niedrig legierten Stahl handelt.

4. Metallguss-Matrix-Verbundwerkstoff gemäß einem der Ansprüche 1 bis 3, der eine Vielzahl von Keramikkuchen umfasst und wobei die Keramikkuchen eine Wabenform aufweisen.

5. Metallguss-Matrix-Verbundwerkstoff gemäß einem der Ansprüche 1 bis 4, wobei die Metallmatrix 2 bis 6 Vol.-% TiC im Vergleich zum Gesamtvolumen der Metallmatrix umfasst.

6. Metallguss-Matrix-Verbundwerkstoff gemäß einem der Ansprüche 1 bis 5, wobei er weitere(s) Metall(e) umfasst.

7. Metallguss-Matrix-Verbundwerkstoff gemäß Anspruch 6, wobei das/die weitere(n) Metall(e) aus duktilen Metallen ausgewählt ist/sind.

8. Gegenstand oder eine Vorrichtung, umfassend einen oder mehrere Metallguss-Matrix-Verbundwerkstoffe gemäß einem der Ansprüche 1 bis 7.

9. Verwendung eines Metallguss-Matrix-Verbundwerkstoffes gemäß einem der Ansprüche 1 bis 7 oder eines Gegenstandes gemäß Anspruch 8 als Verschleißteile, insbesondere für die Zement- und Bergbauindustrie.

10. Verfahren zur Herstellung des Metallguss-Matrix-Verbundwerkstoffes gemäß einem der Ansprüche 1 bis 7, umfassend die folgenden Schritte:

a) Herstellen von Keramikkuchen mittels

- Mischen von Al₂O₃, ZrO₂, FeTi, Graphit und einem Bindemittel, wobei das Bindemittel vorzugsweise ein anorganisches Bindemittel ist, das noch bevorzugter Natriumsilikat, kolloidales Silikat oder eine Mischung davon umfasst,

- Einfüllen der erhaltenen Mischung in eine oder mehrere Vorformlings-Form(en),

- Erwärmen und Aushärten der Mischung, vorzugsweise durch Erwärmen mit einem Mikrowellenofen, einem Infrarotofen oder einem konventionellen Ofen,

- Entfernen der Keramikkuchen aus der/den Vorformlings-Form(en),

- Abkühlen der Mischung auf Raumtemperatur,

b) Gießen des/der Keramikkuchen(s) zu einem Verbundwerkstoff mittels

- Platzieren des/der Keramikkuchen(s) in eine harzartige Form,

- Schließen der harzartigen Form,

- Schmelzen des Metalls, das Eisenmetall und Ferrotitan und Graphit umfasst, um eine Legierung von Metallen zu erhalten, die TiC umfasst,

- Gießen der Metalllegierung in die harzartige Form,

- Erhalten eines Metallguss-Matrix-Verbundwerkstoffes.

11. Verfahren gemäß Anspruch 10, das ferner einen zusätzlichen Schritt (c) aufweist, der Folgendes umfasst:

- Platzieren eines oder mehrerer Abschnitte des aus Schritt (b) erhaltenen Metallguss-Matrix-Verbundwerkstoffes in einer weiteren harzartigen Form,

- Gießen einer weiteren Metallmatrix in die harzartige Form.

12. Verfahren gemäß Anspruch 11, wobei es den folgenden Schritt umfasst:

- Erwärmen des/der Abschnitte(s) des Metallguss-Matrix-Verbundwerkstoffes in die harzartige Form vor dem Gießschritt.

13. Verfahren gemäß Anspruch 10 oder 12, welches darüber hinaus die folgenden Schritte umfasst:

- Ausführen von Gussputzschritten.

14. Verfahren gemäß Anspruch 13, welches darüber hinaus folgenden Schritt umfasst:

- Anwenden einer Wärmebehandlung auf den erhaltenen Metallguss-Matrix-Verbundwerkstoff.

15. Verfahren gemäß einem der Ansprüche 10 bis 14, wobei die Vorformling-Formen Siliziumkernkästen sind.

Revendications

1. Composite à matrice métallique coulée incluant :

- un ou plusieurs gâteau(x) de céramique comprenant : Al₂O₃, ZrO₂, un métal ferreux et TiC, dans lequel les gâteaux de céramique comprennent de 30 à 60% en poids d'Al₂O₃, de 20 à 40% en poids de ZrO₂, de 0,2 à 4% en poids de graphite, de 1 à 20% en poids de FeTi et de 3 à 6% en poids d'un liant par rapport au poids total des gâteaux de céramique avant coulée de la matrice métallique et dans lequel ils comprennent de 2 à 10% en volume de TiC après coulée de la matrice métallique par rapport au volume total de métal dans le gâteau de céramique après coulée de la matrice métallique, et

- une matrice métallique comprenant : un métal ferreux et TiC, dans lequel la matrice métallique comprend de 50 à 90% en poids de métal ferreux par rapport au poids total de la matrice métallique et de 0,1 à 10% en volume de TiC par rapport au volume total de la matrice métallique.

2. Composite à matrice métallique coulée selon la revendication 1 dans lequel le TiC du/des gâteau(x) de céramique et de la matrice métallique est produit par une réaction in situ de FeTi+C, qui conduit à la formation de Fe+TiC.

3. Composite à matrice métallique coulée selon l'une quelconque des revendications 1 à 2 dans lequel le métal ferreux est un fer à forte teneur en chrome, un acier au chrome, des métaux durs au Ni ou un acier faiblement allié.

4. Composite à matrice métallique coulée selon l'une quelconque des revendications 1 à 3 comprenant une pluralité de gâteaux de céramique et dans lequel les gâteaux de céramique ont une forme en nid d'abeilles.

5. Composite à matrice métallique coulée selon l'une quelconque des revendications 1 à 4 dans lequel la matrice métallique comprend de 2 à 6% en volume de TiC par rapport au volume total de la matrice métallique.

6. Composite à matrice métallique coulée selon l'une quelconque des revendications 1 à 5 dans lequel il comprend un autre/d'autres métal/métaux.

7. Composite à matrice métallique coulée selon la revendication 6 dans lequel l'autre/les autres métal/métaux est/sont choisi(s) parmi des métaux ductiles.

8. Article ou appareil comprenant un/des composite(s) à matrice métallique coulée selon l'une quelconque des revendications 1 à 7.

9. Utilisation d'un composite à matrice métallique coulée selon l'une quelconque des revendications 1 à 7 ou d'un article selon la revendication 8 comme pièces d'usure, en particulier pour les industries cimentière et minière.

10. Procédé pour la préparation du composite à matrice métallique coulée selon l'une quelconque des revendications 1 à 7 comprenant les étapes suivantes :

(a) préparation d'un/de gâteau(x) de céramique par

- mélange d'Al₂O₃, de ZrO₂, de FeTi, de graphite et d'un liant, dans lequel le liant est préférablement un liant inorganique, plus préférablement comprenant un silicate de sodium, un silicate colloïdal ou un mélange de ceux-ci,

- remplissage du mélange obtenu dans un/des moule(s) de préforme,

- chauffage et durcissement du mélange, préférablement par chauffage avec un four à micro-ondes, un four à infrarouges ou un four traditionnel,

- démoulage des gâteaux de céramique du/des moule(s) de préforme,

- refroidissement du mélange à la température ambiante,

(b) coulée du/des gâteau(x) de céramique en un composite par

- mise en place du/des gâteau(x) de céramique dans un moule de type résine,

- fermeture du moule de type résine,

- fusion d'un métal comprenant un métal ferreux et du ferro-titane et du graphite afin d'obtenir un alliage de métaux comprenant du TiC,

- coulée de l'alliage de métaux dans le moule de type résine,

- obtention d'un composite à matrice métallique coulée.

11. Procédé selon la revendication 10 qui comprend en outre une étape additionnelle (c) comprenant :

- la mise en place d'une ou plusieurs partie(s) du composite à matrice métallique coulée obtenu à l'étape (b) dans un autre moule de type résine,

- la coulée d'une autre matrice métallique dans le moule de type résine.

12. Procédé selon la revendication 11 dans lequel il comprend une étape de :

- chauffage de la/des partie(s) du composite à matrice métallique coulée dans le moule de type résine avant l'étape de coulée.

13. Procédé selon la revendication 10 ou 12 qui comprend en outre les étapes de :

- mise en œuvre d'opérations d'ébarbage.

14. Procédé selon la revendication 13 qui comprend en outre l'étape de :

- application d'un traitement thermique au composite à matrice métallique coulée obtenu.

15. Procédé selon l'une quelconque des revendications 10 à 14 dans lequel les moules de préforme sont des boîtes à cœur de silicium.

Drawing